Repair or Replace? [Was: Repairing Timex]

From: Dwight Elvey <elvey_at_hal.com>
Date: Tue Jul 18 12:31:01 2000

Hi
 One method that has not been talked about too much is
one that I've often used. It does take a prom programmer
and an assembler helps. I often write small pieces of
test code to check one part or another of a micro system
and program an eprom with it. While I usually make an assembler
for the processor I'm playing with, the code chunks are so
small that one could easily hand assemble. ( Of course,
if you just happen to have the right ICE or ROM-ICE, you
don't need the programmer. Oh I wish!! )
 I usually try to find some output someplace to use as a
trigger or if you are luck, a display of some kind. Once
one has some kind of basic indicator ( it can be as simple
as a LED light ) one can systimatically test each part
of the system. Some processors that have a lot of registers,
like the Z80 can run without RAM, making RAM test without
any system RAM used by the program.
 I use this method on old computers as well as on pinball
machines ( an other hobby ). It helps to have schematics
but if you understand the basic layout of the machine and
have data books for some of the LSI I/O chips, it doesn't
take long to write useful test code.
Dwight
Received on Tue Jul 18 2000 - 12:31:01 BST